1. Field of the Invention
This invention relates to improvements in a method and apparatus for bleeding off the fluid boundary layer in rotating compressor apparatus.
2. Description of the Prior Art
For advanced axial compressor rotors and centrifugal compressor inducers, shock-boundary layer interaction in the entry region can cause unacceptable boundary layer growth. High boundary layer blockage levels are generally associated with reduced performance for these turbomachines, and it has long been recognized that rotor performance gains would result if boundary layer bleed could be used. For example, U.S. Pat. No. 2,720,356 to Erwin discloses a system for continuous boundary layer control in axial compressors associated with aircraft gas turbine engines, and U.S. Pat. No. 4,248,566 to Chapman et al. describes a boundary layer bleed system for a centrifugal compressor.
In several reports on centrifugal compressors, the rotor flow is reported to separate in the suction side/shroud corner of the flow path where it turns radial. The static pressure at the critical location in the compressor housing (suction side/shroud corner) is generally low compared to compressor inlet pressure. Further, the blade-to-blade static pressure difference is such that conventional boundary layer extraction slots would bleed off most of the flow from the (not critical) pressure side of the blade. Frequently, therefore, the total amount of bleed fluid extracted to achieve boundary layer control on the suction sides is excessive and/or the work required to extract (or bleed) boundary layer fluid does not produce the desired theoretical increased overall efficiency.
The present invention is related to improving the suction side boundary layer bleed characteristics as applied in turbomachines of different kinds to achieve increased efficiencies. In gas turbine engines where bleed flow is required outside the compressor component, cycle benefits may result if these fluid bleed flows are used, for example to achieve cooling, in addition to the improved compressor performance. Application of the present invention will enhance the performance gains associated with such applications.